This invention relates to photographic paper supports and more particularly to photographic paper supports having polyethylene resin layers on both sides.
The photographic support rolls are coated with photographic emulsion to be made into photographic paper rolls, which in turn are printed, developed, and finally cut into sheets of a predetermined size. Said cutting step is automated and this automatic cutting step has to be facilitated by perforating a hole or putting a mark on the photographic paper surface at a preceding step so that exact cutting positions are established. Hitherto, because of poor cutting property of the supports at the perforating and cutting steps, there often occur such problems as irregular cut edges, generation of paper dusts, in an extreme case incomplete cutting or hanging of waste debris onto the cut paper sheet and in the worst case unseparation of the paper sheets. Furthermore, in the case of providing a hole of about 0.5-1 mm as a cutting mark, the hole is filled up with trailing or whiskering of fibers or polyethylene resins of the support thus cannot be detected by a photocell resulting in the incomplete cutting or miss cutting very often. One way to solve this trouble is to always maintain the cutting or the perforating knife sharp. In order to do so, sharpness of the knives have to be checked constantly and the knife blades be changed frequently. This knife maintenance is hard and cumbersome, necessitates frequent shutdowns for knife change, therefore lowers productivity and increases costs. Therefore, such photographic supports of improved cutting property that would assure longer span of the knife repairs have been much demanded.
Furthermore, a light weight photographic polyethylene coated paper has been desired for convenience of handling and for reduction of freights, postages and costs for woodpulps and other materials. However, there is a problem that the lighter the photographic support papers are made to, the less stiff they become.
It is necessary for obtaining photographic polyethylene coated papers having good cutting properties at the cutting and perforating steps to reduce long fiber furnish as far as possible. However, hitherto, production of light weight photographic support papers having stiffness as high as that of ordinary weight papers requires furnish of long and strong woodpulp fibers such as softwood bleached kraft pulp (NBKP) or softwood bleached sulfite pulp (NBSP).
Trailing or whiskering of fibers at cut edges of supports occurs more or less regardless of length of fibers contained in the supports, but there is a tendency that longer the fibers, the more it occurs. Especially, light weight resin coated papers having, for example, a basis weight of less than 160 g/m.sup.2, especially less than 150 g/m.sup.2 are required to have increased stiffness and for this purpose it is preferred to use long and strong fibers in a large amount. Thus, it is earnestly desired to reduce formation of trailing or whiskering of fibers at cut edges.
The inventors, as a result of intensive researches on the improvement of supports, have found photographic supports which have extremely improved cutting properties at perforating or cutting steps.